Microstructure and PTCR characteristics of porous BaTiO3-based ceramics prepared by adding activated carbon

As a pore precursor, activated carbon of different contents (0 to 30 vol%) was added to (Ba,Sr)TiO₃ powder. Porous (Ba,Sr)TiO₃ ceramics were prepared by pressureless sintering at 1350 °C for 1 h in air. The effects of the activated carbon content on the microstructure and positive temperature coefficient of resistivity (PTCR) characteristics in porous (Ba,Sr)TiO₃ ceramics were investigated. The porosity of the porous (Ba,Sr)TiO₃ ceramics increased from 6.5% to 33.5%. The PTCR jump of the porous (Ba,Sr)TiO₃ ceramics prepared with activated carbon was > 10⁵ and increased slightly with increasing activated carbon concentration. These results correspond to the Heywang model of the PTCR effect in (Ba,Sr)TiO₃ ceramics, suggesting that activated carbon is an effective additive for preparing porous BaTiO₃-based ceramics. The newly prepared (Ba,Sr)TiO₃ ceramics can be used as a gas sensor.